<template>
 <div class="s-canvas">
    <canvas id="s-canvas" :width="contentWidth" :height="contentHeight"></canvas>
 </div>
</template>
<script>
export default {
 name: 'SIdentify',
 props: {
 identifyCode: {
  type: String,
  default: '1234'
 },
 fontSizeMin: {
  type: Number,
  default: 25
 },
 fontSizeMax: {
  type: Number,
  default: 30
 },
 backgroundColorMin: {
  type: Number,
  default: 255
 },
 backgroundColorMax: {
  type: Number,
  default: 255
 },
 colorMin: {
  type: Number,
  default: 0
 },
 colorMax: {
  type: Number,
  default: 160
 },
 lineColorMin: {
  type: Number,
  default: 100
 },
 lineColorMax: {
  type: Number,
  default: 255
 },
 dotColorMin: {
  type: Number,
  default: 0
 },
 dotColorMax: {
  type: Number,
  default: 255
 },
 contentWidth: {
  type: Number,
  default: 112
 },
 contentHeight: {
  type: Number,
  default: 31
 }
 },
 methods: {
 // 生成一个随机数
 randomNum(min, max) {
  return Math.floor(Math.random() * (max - min) + min)
 },
 // 生成一个随机的颜色
 randomColor(min, max) {
  let r = this.randomNum(min, max)
  let g = this.randomNum(min, max)
  let b = this.randomNum(min, max)
  return 'rgb(' + r + ',' + g + ',' + b + ')'
 },
 drawPic() {
  let canvas = document.getElementById('s-canvas')
  let ctx = canvas.getContext('2d')
  ctx.textBaseline = 'bottom'
  // 绘制背景
  ctx.fillStyle = this.randomColor(this.backgroundColorMin, this.backgroundColorMax)
  ctx.fillRect(0, 0, this.contentWidth, this.contentHeight)
  // 绘制文字
  for (let i = 0; i < this.identifyCode.length; i++) {
  this.drawText(ctx, this.identifyCode[i], i)
  }
  this.drawLine(ctx)
  this.drawDot(ctx)
 },
 drawText(ctx, txt, i) {
  ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax)
  ctx.font = this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei'
  let x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
  let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5)
  var deg = this.randomNum(-45, 45)
  // 修改坐标原点和旋转角度
  ctx.translate(x, y)
  ctx.rotate(deg * Math.PI / 180)
  ctx.fillText(txt, 0, 0)
  // 恢复坐标原点和旋转角度
  ctx.rotate(-deg * Math.PI / 180)
  ctx.translate(-x, -y)
 },
 drawLine(ctx) {
  // 绘制干扰线
  for (let i = 0; i < 5; i++) {
  ctx.strokeStyle = this.randomColor(this.lineColorMin, this.lineColorMax)
  ctx.beginPath()
  ctx.moveTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
  ctx.lineTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
  ctx.stroke()
  }
 },
 drawDot(ctx) {
  // 绘制干扰点
  for (let i = 0; i < 80; i++) {
  ctx.fillStyle = this.randomColor(0, 255)
  ctx.beginPath()
  ctx.arc(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight), 1, 0, 2 * Math.PI)
  ctx.fill()
  }
 }
 },
 watch: {
 identifyCode() {
  this.drawPic()
 }
 },
 mounted() {
 this.drawPic()
 }
}
</script>
<style scoped>
.s-canvas {
 height: 40px;
}
.s-canvas canvas{ 
 margin-top: 5px;
 margin-left: 3px;
}
</style>